Preparation of 2-chloro-4-methoxy-5-nitro-toluene and 2-chloro-4-methoxy-5-aminotoluene

ABSTRACT

5-Nitro-4-alkoxy-2-chlorotoluene, wherein the alkoxy group contains 1 to 2 carbon atoms, is prepared by reacting 5-nitro-2,4-dichlorotoluene with the desired alkali metal alcoholate in the presence of the corresponding alcohol at a temperature from 65 DEG  to 80 DEG  C., the amount of said alcoholate not exceeding 1.1 mol. per mol. of 5-nitro-2,4-dichlorotoluene.  In the preferred method, equimolecular quantities of reactants are used.  The resulting compound may be reduced to the corresponding 5-amino-4-alkoxy-2-chlorotoluene, e.g. with acetic acid and zinc. The Specification also states that 5-amino-4-methoxy-2-chlorotoluene has been prepared by acylating 2-methoxy-5-methylaniline, e.g. introducing the acetyl or oxalyl radical, chlorinating the resulting acylated compound and hydrolysis of the acylamino group in the resulting 5-acylamino - 4 - methoxy - 2 - chlorotoluene. 5-Nitro-2,4-dimethoxytoluene by heating 5-nitro-2,4-dichlorotoluene with sodium methylate in methanol at 115/120 DEG  C., the amount of alcoholate being approximately 2 mols. per mol. of dichlorotoluene. 5-Nitro-2,4-dichlorotoluene by the action of concentrated sulphuric and nitric acids on 2,4-dichlorotoluene.  5 - Nitro - 1 - chloro - 2 : 4 - dimethoxy benzene is obtained by heating 5-nitro-1,2,4-trichlorobenzene and approximately two mols. of sodium methylate in methanol.

Patented Jan. 8, 1952 UNITED STA-rois Bernard William Rottschaefer,

SSignOr to General Anviline & Film Con- East Greenbush,

poration, New York, N. Y., a corporation of Delaware No Drawing. Application December 22, 419.48, serial No. 66,828

8 Claims- 1 This invention vrelates te the preparation of nitrofflfakoXyfZfchlorotoluenes and the oo rrespending S-amlno-l-alkoxy 2 chlorotoluenes.. More particularly, the invention relates to the preparation of 5-n itro4 -methoxy2 chlorotoluene and -nitroei-ethoxy-2fohlorotoluene, and the corresponding omino compounds- In accordance with iny invention, the aforeseid nitro compounds, which constitute new compositions .of matter, are prepared by reacting 5.- nitro-Zfl-diohlorotoluene with an 'alkali ,metal alcoholate (i. e. sodium .or potassium methylate or ethylete) in .the oor-,responding alcohol es e medium, at temperatures cubista tially .Within the range lid-89 the amount of said alcoholate not substantially exceeding L1 molecular equivalent Per mol oi `5-nitro=2,i-diohlorotoluene. Thus, the amount o f alkali metal alcohols ete employed in the reaction mixture should not exceed Ll mol per mol of 5-nitrof24-,diohlorof toluene. The 5-nitro-ifellsoxyf2=oh1orotoluenes produced in the aforesaid reaction .can be ree covered Afrom the reaction mixture, for example, hy dilution with water and filtering out the pref cipitated reaction product, or by cooling the reaction mixture .to efieot crystallization of the product therefrom rvand separation of the Produot from the mother liquor. When equimolecu lai' amounts of the reagents are used, substantia-ily quantitative yields of d-nitro--allsoxy-.Z- ohlorotoluenes are .obte-ined by aqueous precipitation and washing. The product thus recovered is of high purity, adequate for use as an inter.-` mcdiate for dyestuls and other dyestuff inter,- mediates without further purification. Thus, the 5-nitro-4-alkoXy-Z-ohlorotoluenes Produced according to my process can be reduced to the oo lresponding ,-5-einino compounds, e. g. by reduction with Zinc end acetic acid.. The .amino compounds thus obtained can be diazotized in the usual manner, by treatment with nitrous acid or compositions yielding the same, and coupled with czo coupling components for the production of azo dyestuffs.

It was known heretofore to prepare 5-aminotfinetnoxyfzfchloroioluene by s process invoiving acylatlon of the amino group of residine (i, e. 2-methoxy-5methylaniline), e. g. by introduction of an acetyl or .oxalyl radical, chlorination of the resulting acyla-ted compoundz and hydrolysis of the @Leyla-mino group in the resulting 5sacylamino-l-metlroxy' 2 f -ohlorotoluene However, this procedure requires a relatively expensive starting materia-l, is relatively complicated in that it involves aeylation and saponine cation step, and is wasteful in that the acyl rade ical is eliminated and .lost in .the saponincation. The process of this invention employs a rela- (Cl, Z50-,612)

tively inexpensive starting rnaterlal (produced by dichlorinatlon and nitration of toluene), and involves e simple alzkexvlat-ion step followed by reduction of the nitro grou-P- Seleo-tive replacement of the chlorine ooounying the ll.-positionin 5,-nitro-2,4-dichlorotoluene by an vallfrony group as it occurs in the process of this invention, -to form the 4-alkoxy derivative, constitutes a surprising and unexpected result, since the clfijlorine atom Vin the -Zfposition is also vreactive toward alkali metal alcoholates. Thus, :Dadswell et al. (J, C. iS. 1927,11. 58,5) ydist-:loses that 5nitro-2,4 fdiinethoxytoluene is formed by heating 5-vnl-tro.2,4edichlorotoluene with sodium meth-.viste in methanol solution et L15-120 C., the amount of eloonolate beine approximately 2 .mois per mol of .5-nitro2,4ediohlorotoluene, In the analogous reaction of 5-nitro- L-2A-trichlorobenzene with .sodium methylate, the corre spend-ing Z-.dimethoxy derlvativeis likewise obtained, .as disclosed in German Patent 135,331. However, if only 1 rnol ,ofv alkali metal methyI- ate is reacted with 5-nitro-1(,2,4etrichloroben zene, difdcu-ltly ,separable mixture of different reaction products is obtained v according to the aforesaid German notent. while according to Hollexnan .et al. (Rec, d0, 19,2;1, pgs. f77-'78), the chlorine in the 2-position rather than the 4-position is selectively replaced by a methoxyl group. Thus, the fact that selective replacement of chlorine occurs in the process of this invention, and the further fact that the chlorine atom in the A- 11; osition rather than in the 2position of 5nitros2l-diehlorotoluene `is selectively replaced Yby the alkoxyl group, is contrary to expectation.

Preferred methods :for carrying out the prooess o f my invention are illustrated in the following examples, wherein parts and percentages are by weight and temperatures are in degrees centigradev5fnitro-2,4oliohlorotoluene is prepared by mixing 161 parts 1 mol) of 2,4.-dichlorotoluene with 1G60 parts of concentrated sulfuric acid at 0-5", and slowly adding ,mixed acid .(1. e. a mixture of 36% concentrated nitric acid 61% concentrailed sulfuric acid) containing 'the vequivalent of 1 mol of nitric acid to the cooled sulfuric acid mixture with good agitation. When the nitration is complete, the reaction mixture is drowned in a mixture of ice and, water, and the product thereby precipitated is isola-ted by filtration. The 5-nitro-2,4-dichlorotoluena ,thus recovered, can be purified, if desired, by jrecrystall-izat-ion from methanol.

207 parts (l mol) o f 5-nitro-2,4dich1orotoluene were dissolved in 400 parts of methanol. A solution of 40 parts of flaked sodium hydroxide in 400 parts of methanol were added. The mixture was gradually heated to boiling temperature (about 67) under reflux for several hours. 700 parts of methanol were then removed from the mixture by distillation. The residual reaction mixture was poured into water and the 5- nitro-Li-methoxy-2-chloroto1uene thereby precipitated was recovered by ltration, and washed with water. An almost quantitative yield was thereby obtained.

By treatment of the product with zinc and aqueous acetic acid, the nitro group was reduced to an amino group, yielding 5-amino-4-methoxy- 2-chlorotoluene, identical with that obtained by chlorination of acylated cresidine and hydrolysis of the acylamino group. f

Example 2 206 parts (1 mol) of 5-nitro-2,4dichlorotoluene were added to a solution of 56 parts (1 mol) of potassium hydroxide in 950 parts of methanol at 45. The mixture was heated to boiling under reiiux (67) for 48 hours, and then cooled to 5. The product which crystallized out was separated by filtration and washed with 400 parts of 70% aqueous methanol at -5". The product was then slurried with 700 parts of water, separated from the water by iiltration, washed with water, and dried at about 40. Upon analysis, the chlorine contentwas found to be 17.9%, as compared with theoretical value of 17.6%, Aindicating that the product had a purity of about 98-99%. The product was recovered in the form a a light yellow nely crystalline powder identical in composition with that obtained in Example 1.

Upon reduction of the product as described in Example 1, to the corresponding amino compound, kamino4-methoxy2-chlorotoluene was obtained, which upon diazotization and coupling with a series of azo coupling components, yielded dyestuffs identical to those similarly produced with a known sample of 5-amino-4-methoxy-2- chlorotoluene obtained by previously known prior art processes.

By substituting ethanol for methanol in the alkylation reaction of the foregoing examples, and' heating the mixture to a reaction temperature within the range 65-80" C., the corresponding 5-nitro4-ethoxy-2-chlorotoluene can be 0btained, which likewise yields the corresponding amino compound on reduction with zinc and acetic acid.

The alkali metal alcoholate employed in the alkylation reaction of this invention can be prepared either by dissolving an alkali meta-l hydroxide in the corresponding alcohol or, if desired, it can be made by reacting an equivalent amount of alkali metal with the alcohol.

Equimolecular amounts of alkali metal alcoholate or alcoholic alkali metal hydroxide solution and of 5-nitro-2,4dichlorotoluene are preferably employed. However, at the aforesaid temperature range of 65-80" C., a slight excess '(up to 10%) of alkali metal alcoholate does not impair the purity of the product. Use of less than equimolecular amounts of alkali metal alcoholates, however, yields mixtures of 5nitro4 alkoxy-Z-chlorotoluene with unreacted 5-nitro- 2,4-dichlorotoluene which are relatively inconvement to separate, and reaction under these conditions is preferably avoided.

The products obtained are of suicient purity to serve as azo dyestuff intermediates Without special puriiication other than precipitation and washing. However, if further purication is desired, it' can be effected by recrystallizing the 5-nitro-4-alkoxy-Z-chlorotoluenes from organic solvents, e. g., from alcohol.

Variations and modifications which will be obvious to those skilled in the art can be made in the foregoing-'procedure without departing from the scope or spirit of the invention.

I claim:

1. A process for the preparation of 5-nitro-4- alkoxy-Z-chlorotoluene, wherein the alkoxy group contains 1-2 carbon atoms, which comprises reacting 5-nitro-2,4dichlorotoluene with an alkali metal alcoholate, of the class consisting of alkali metal methylates and alkali metal ethylates, in the corresponding alcohol as a medium, at a temperature from 65-80 C., the amount of said alcoholate not substantiallyexceeding 1 mol per mol of 5-nitro2,4dichloro toluene. y y

2. A process for the preparation of 5-nitro-4- alkoxy-2-chlorotoluene, wherein the alkoxy group contains 1-2 carbon atoms, which comprises reacting 5-nitro2,4dichlorotoluene with a substantlially equimolecular amount of an alkali metal alcoholate, of the class consisting of alkali metal methylates and alkali metal ethylates, in the corresponding alcohol as a reaction medium at a temperature from G35- 80 C.

3. A process for the preparation of 5nitro4- methoxy-2-chlorotoluene, which comprises reacte ing 5-nitro-2,4-dichlorotoluene with a substantially equimolecularamount of an alkali metal methylate in methanol as a reaction medium at a temperature from 65-80 C.

4. AV process for the preparation of 5-nitro4- ethoxy-2-chlorotoluene, which comprises reacting 5-nitro-2,4dichlorotoluene with a substan tially equimolecular amount of an alkali metai ethylate in ethanol as a reaction medium at a temperature from 65-80 C.

5. A process for the preparation of 5-amino4 alkoxy-Z-chlorotoluene, wherein the alkoxy group contains 1-2 carbon atoms, which comprises reacting 5-nitro-2,4dichlorotoluene with an alkali metal alcoholate, of the class consisting of alkali metal methylates and alkali'metal ethylates, in the corresponding alcohol as a reaction medium at a temperature from {i5-80 C., the amount of said alcoholate not substantially exceeding 1 mol per mol of 5-nitro2,4dichloro toluene, separating 5-nitro-4-alkoxy-2-chlorotoluene from the reaction mixture, and reducing the nitro group to an amino group.

6. 5-nitro-4-alkoxy-2-chlorotoluene, wherein the alkoxy group contains 1-2 carbon atoms.

7. 5-nitro-4-methoxy-2-chlorotoluene 8. 5-nitro-4-ethoxy-2-chlorotoluene.

BERNARD W. ROTTSCHAEFER.

REFERENCES CITED The following references are of record in the file of `this patent:

UNITED STATES PATENTS Number Name Date 695,812 Julius et al. Mar. 18, 1902 1,564,214 Derick et al. Dec. 8, 1925v 2,007,234 Wirth July 9, 1935 2,056,261 `Dahlen et al. l Oct. 6, 1936` 2,186,367 Coleman et al Jan. 9, 1940 2,312,801 Craig et al. Mar. 2, 1943 2,370,524 penison et al. Feb. 27, 194.5` 

1. A PROCESS FOR THE PREPARATION OF 5-NITRO-4ALKOXY-2-CHLOROTOLUENE, WHEREIN THE ALKOXY GROUP CONTAINS 1-2 CARBON ATOMS, WHICH COMPRISES REACTING 5-NITRO-2,4-DICHLOROTOLUENE WITH AN ALKALI META ALCOHOLATE, OF THE CLASS CONSISTING OF ALKALI METAL METHYLATES AND ALKALI METAL ETHYLATES, IN THE CORRESPONDING ALCOHOL AS A MEDIUM, AT A TEMPERATURE FROM 65-80* C., THE AMOUNT OF SAID ALCOHOLATE NOT SUBSTANTIALLY EXCEEDING 1 MOL PER MOL OF 5-NITRO-2,4-DICHLOROTOLUENE. 